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June 9,- 1953 c. THUMIMk RESONANT SILENCER Original Fladdan. 3, 1949 2Sheets-Sheet 1 INVENTOR. BY aJd @umd/m,

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June 9, 1953l c.,rHUM|M Re- 23,567

RESONANT SILENCER I original Filed Jan. s, 1949 2 Sheets-Sheet 2 IN VENTOR: @animi/numb -the lag depending on Reissued June 9, 1953.

caser REsoNAN'r SILENcEa Carl Thumiin, Yeadon, Pa.,

assignor to I-'LE Circuit Breaker Company, Philadelphia, Pa., acorporation oi' Pennsylvania Original No. 2,585,600, dated February 12,1952,

Serial No. 68,831, January for reissue February 11, 1953, Serial No.

(Cl. G-91) brackets I: Il appears in the original patent but forms nopart o! this reissue specication; matter printed in italics indicatesthe additions made by reissue.

1 Claim.

Matter enclosed in heavy solenoids, undervoltage devices, and relays es--pecially when they are equipped with time delay devices forpurposefully retarded operation.

In any magnetic device operating on alternating current, the fluxfollows the current closely, the characteristics of the force betweenthe stationthe moving armature,

steel. The attractive ary magnetic frame and however, does not changesign, is always positive and in attempting to follow the ilux contour,it results in a force curve with a rippled upper boundary which may bebroken up into a continuous force and an oscillating force, the latterhaving an approximately sinusoidal shape with a frequency twice thefrequency of the circuit to which the device is attached. The shape ofthe wave is analogous to that of an offset alternating current wavewhich may be broken into a symmetrical wave and a direct currentcomponent.

At the point at which the armature is calibrated to move, the combinedweight of the armature and its attached parts plus the force of thespring when used is exactly balanced by the RMS value of the magneticforce. Any change in the relationship betwe'en the two sets of forceswill `cause the armature to move in the direction of the larger force.Since the force curve of the magnet is sinusoidal in form, the armaturetends to move in accordance with the resultant force, thecharacteristics of the motion depending on the combination of -massesand springs involved. Even slight motion of the armature takes up slackin one direction and then in the other between itself and the attachedparts, especially when the latter are connected to a time delay device,between itself and the mounting pivot and between itself and thecalibrated stop.

The result is an annoying buzz and sometimes a loud clatter. A number ofdevices in one installationjwhich is not uncommon, may result in enoughnoise to mask other signals. This constitutes a hazard in addition tothe physiological effects on the operating personnel. In addition, thechattering results in wear on parts, eventually causing change ofcalibration or, in the worst conditions, failure.

The primary object of my invention is the provision of apparatus forovercoming or coun- 3, 1949. Application 336,465

terbalancing the tendency of the armature to vibrate.

More specically, I provide a tuned mechanical system consisting of aweight at the end of the spring rmly attached to the armature.

This system should be undamped and should have a resonant frequencyequal to that of the impressed force, i. e., twice the circuitfrequency. Being in resonance, even the slightest motion of the armatureis immediately amplilied linto a large vibration of this system whichabsorbs all the energy tending to make the armature vibrate.

The foregoing and many other objects of my invention will becomeapparent in the following description and drawings in which:

Figure 1 is a side view of a circuit breaker hav'- ing a time delaytripping armature with the resonant silencer unit attached to thearmature thereof.

Figure 2 is an enlarged view of the armature and its resonant silencerunit.

Figure 3 is a view in perspective of the resonant silencing element tobe attached to the armature.

Referring now to the gures, I have shown my novel resonant silencerattached to the armature of a circuit breaker, although it will beobvious that the resonant silencer may be attached to the armature ormovable element of any alternating current device in which the problemsof noise, chatter, or vibration are encountered.

The circuit breaker shown in Figure 1 is substantially a. standardcircuit breaker of wellknown commercial type having an upper backconnection stud I0 carrying a main stationary contact II and astationary arcing contact I2 which are engaged in time by the movablemain contact I3 and the movable arcing contact I4 which operate in thearc chute I5.

Blow-out coil I6 is provided in the arc chute I5, and appropriatecircuit connections are made (not shown) to energize the blow-out coilduring the opening of the circuit breaker.

Current passes through the movable Contact arm Il and pigtail I8 toterminal I9 of the series trip coil 2D, through the series trip coil 20to the lower back connection stud 2I.

`Appropriate operating mechanism 22 is provided for closing the circuitbreaker, the operating mechanism being connected by link 23 to crank 24on the shaft 25 which carries the movable contact I1.

A suitable opening bias is provided for the movable contact arm Iltending to pull the movable contacts away from the stationary contacts.and the operating mechanism 22 is provided with suitable latch means formaintaining the elements thereof in closed circuit position against thebias of the opening spring.

The latch mechanism is so arranged that it will be tripped by rotationof thelatch trip bar 3l) to permit the opening bias to open the circuitbreaker contacts. The latch trip bar 30. and its extension 3l are soarranged that they will be engaged by the roller 32 of the extension 33of armature 34 which is pivotally mounted on pin 35 when the armature 34is attracted toward the trip coil 2li and its magnet 36 on appropriateenergization of coil 20. V

The armature 34 is of a standard type wherein the main portion thereofis of magnetizable material so that it may be attracted by the magneticflux generated by trip coil 20 and the magnetic material 3B of thetripping unit.

The armature is restrained and calibrated for movement only on theoccurrence of an overcurrent condition of predetermined minimum value(and, therefore, on the occurrence of a magnetic flux of predeterminedminimum value) by the tension spring 40 connected between lug 4I on thearmature and nut 42 on the rotatably mounted Calibrating screw 43.

The armature 34 is also connected by pin 45 to sleeve 46 which in turnis connected to the upper sucker disc 41 in the time delay dashpot 48.

The sleeve 46 may also have a quick trip compression spring 49 inaccordance with the disclosure contained in Patent No. 2,486,594, issuedNovember l, 1949, assigned to the assignee of the present invention.

As above pointed out, particularly in those instances where the movementof the armature is time delayed as the current value at which thearmature is calibrated to move to trip position is approached (but notreached) the sixty cycle alternating current generating a similarvariation in magnetic flux tends to cause the armature 34 to vibrate ata frequency of one hundred and twenty cycles per second producing achatter and noise combined with a low pitch hum.

My invention contemplates providing a resonant inertia member andattaching the same to the armature, the said resonant inertia memberbeing tuned to have a period oi vibrationidentical with that of thearmature and the fsecurement of the inertia member being so arrangedthat its vibration will always be in opposite phase to that of thearmature whereby the movement of the armature in one direction will becounterbalanced by the movement or vibration of the resonant inertiamember in the opposite direction.

For this purpose I provide the double pronged leaf spring member 5Uhaving the securing section 5I and the legs 52, 53. Section 5l issecured to the armature in any suitable manner as, for

v small segments so that adjustments may readily be made by adding orremoving weights until the mass of the weights 64 is adjusted so thatthe spring members 52, 53 are tuned to have a period of vibration of onehundred and twenty cycles per second or exactly equal to the period ofvibration of the armature 34 when subjected to a high current conditionshort of the over-current condition for which the unit is to operate.

In another embodiment, the structure consists of a fixed mass fastenedto a. spring which is adjustable as to length from the mass to the ilxedpoint. The principle to be maintained is that the combination of massand spring must have a natural frequency which is the same as that 0fthe disturbing force and, therefore, is in resonance with it.

With the period of vibration of the spring 5U tuned to be resonant withthe period of vibration of the armature 34 induced therein by thevariations in magnetic iiux owing to the variations in current, then thepositioning of the spring member 50 and of the weights 64 is such thatthe vibration of the spring 5D will always be in opposite phase to thevibration of the armature 34, thereby damping or cancelling out thevibration of the armature 34-or rather the vibration of the two elementsin opposite phase cancel each other out to produce no net vibration atall.

The reason for this is that as armature 34 is drawn upwardly at or nearthe positive peak Of a sixty cycle sign wave, the initial inertia of themass 64 causes it to remain stationary in space and, therefore, to movein an opposite direction with respect to the movement of the armature34.

ural period of vibration of the spring 50 and weights 64 and the inertiaof these members will now cause these members to be once more stationaryin space but, therefore, in condition where they are moving away fromthe armature 34.

Thus, the vibration of the armature 34 results in an equal and oppositevibration of the spring 50 and its weights 64. This is so because theinitial vibration of the armature 34 tends to start the spring 50 andits elements in vibration in opposite phase; and since the spring andits weights 64 are tuned to vibrate at the same frequency as thearmature 34, this opposite relationship will always be maintained.

The natural condition for these units is an opposite phase relationshipsince each vibration of the armature 34 tends to move the armature 34away from the weights or masses 64 so that each of these elements tendsto be out of phase with the other and since they are in tune this out ofphase relationship will be maintained` The actual result, however, isthat with two masses thus opposing each other at the same frequency theycancel each other out to produce a noiseless vibrationless system. Theonly time a noise or sound will be encountered is when there is aviolent change in the current and, therefore, the ilux which attractsthe armature.

The system will vibrate, hum or make a noise momentarily until the newcondition levels oil with the resonant spring or inertia unit dampingout the vibrations of the armature and vice versa.

Thus, where a circuit breaker is-set to trip at three times normal, thenas long as the current stays at or near normal no vibration will beheard. This has been found by actual experiment to be the case.

Should the current suddenly change to twice normal. a momentary hum willensue owing to the violent change in the amplitude of induced vibration,but this will bedamped out almost immediately by the two forces whichoppose each other, to wit, the armature and the spring.

Should the current suddenly change to three times normal or more, thenthe ilrst violent reaction which pulls the armature up will, owing tothe setting of the calibrating screw, permit the armature to tripthecircuit breaker. If the armature does not trip the circuit breaker atthis iirst violent reaction to a change in the current value, then thespring which is brought into movement of equal and opposite force inresonance with the armature quickly damps out the vibrations of thearmature at this changed force.

Accordingly, the circuit breaker may be adjusted for any tripping valueand if it is adjusted to trip at ten times normal, then thearmaturevibrations are damped out at any value up to ten times normal,while when the ten times normal condition is reached the entire systemis pulled up sufficiently to trip the elements.

Thus, my invention has particular applicability to time delayed andcalibrated systems where an armature may hang on or oat when the currentvalue approaches the trip point without quite reaching it, producing theunpleasant noise and vibration.

My novel system by damping out this noise or vibration at any valuebelow the tripping point and permitting a trip to occur at the trippingpoint ensures positive and accurate operation of the armature, and cutsout the noise and the wear incident therewith.

In the foregoing I have described my invention solely in connection withspecific illustrative embodiments thereof. Since many variations and 6modifications of my invention will now be obvious to those skilled inthe art, I prefer to be bound not by the specific: disclosures hereincontained but only by the appended claim.

I claim:

In a circuit breaker for use in a circuit carrying cyclically pulsatingcurrent having a pair of cooperable contacts, a trip magnet responsiveto predetermined currents for effecting disengagement of said contacts,said magnet having an armature, said armature having [movement]vibration in response to less than said predetermined currents, acalibrated biasing means for restraining said armature for movement tofull trip position only in response to energization of said magnet bysaid predetermined current and a resonant inertia member attached tosaid armature and having the same period of vibration as said'[cyclically pulsating current] armature, said inertia member comprisinga double pronged leaf spring secured to said armature at one end andhaving legs at the other end and a plurality of weights secured to saidlegs, the connection of said inertia member to said armature being suchthat said inertia member vibrates out of phase with said armature, andrestrains movement of said armature at currents less than saidpredetermined currents.

CARL THUMIM.

References Cited in the le of this patent or the original patent UNITEDSTATES PATENTS Number Name Date 667,106 Thomson et al. Jan. 29, 1901819,559 La Cos May l, 1906 1,014,257 Rosenqvist Jan. 9, 1912 1,425,700Scott Aug. 15, 1922 1,798,922 Ytterberg Mar. 31, 1931 2,265,297 Little 1Dec. 9, 1941 2,340,973 May et al. Feb. 8, 1944 2,419,892 Graves, Jr.Apr. 29, 1947 2,439,165 Graves, Jr. Apr. 6, 1948

